"Turn Off" binmode(STDOUT, ":utf8") Locally - perl

Question

I Have The following block in the beginning of my script:
#!/usr/bin/perl5 -w
use strict;
binmode(STDIN, ":utf8");
binmode(STDOUT, ":utf8");
binmode(STDERR, ":utf8");
In some subroutines when there is other encoding(from a distant subroutine), the data will not display correctly, when receiving cyrillic or other characters. It is the "binmode", that causes the problem.
Can I "turn off" the binmode utf8 locally, for the subroutine only?
I can't remove the global binmode setting and I can't change the distant encoding.

Answer 1

One way to achieve this is to "dup" the STD handle, set the duplicated filehandle to use the :raw layer, and assign it to a local version of the STD handle. For example, the following code
binmode(STDOUT, ':utf8');
print(join(', ', PerlIO::get_layers(STDOUT)), "\n");
{
open(my $duped, '>&', STDOUT);
# The ':raw' argument could also be omitted.
binmode($duped, ':raw');
local *STDOUT = $duped;
print(join(', ', PerlIO::get_layers(STDOUT)), "\n");
close($duped);
}
print(join(', ', PerlIO::get_layers(STDOUT)), "\n");
prints
unix, perlio, utf8
unix, perlio
unix, perlio, utf8
on my system.

Answer 2

I like #nwellnhof's approach. Dealing only with Unicode and ASCII - a luxury few enjoy - my instinct would be to leave the bytes as is and selectively make use of Encode to decode()/encode() when needed. If you are able to determine which of your data sources are problematic you could filter/insert decode when dealing with them.
% file koi8r.txt
koi8r.txt: ISO-8859 text
% cat koi8r.txt
������ �� ����� � ������� ���. ���
���� ����� ������ ����� �����.
% perl -CO -MEncode="encode,decode" -E 'say decode("koi8-r", <>) ;' koi8r.txt
Американские суда находятся в международных водах. Япония

Answer 3

You could use something like Scope::Guard - lexically-scoped resource management to ensure it gets set back to :utf8 when you leave the scope, regardless of how (return, die, whatever):
#!/usr/bin/perl -w
use strict;
use Scope::Guard qw(guard);
binmode(STDOUT, ':utf8');
print(join(', ', PerlIO::get_layers(STDOUT)), "\n");
{
# When guard goes out of scope, this sub is guaranteed to be called:
my $guard = guard {
binmode(STDOUT, ':utf8');
};
binmode(STDOUT, ':raw');
print(join(', ', PerlIO::get_layers(STDOUT)), "\n");
}
print(join(', ', PerlIO::get_layers(STDOUT)), "\n");
Or, if you don't want to include a new dependency like Scope::Guard (Scope::Guard is awesome for this kind of localizing...):
#!/usr/bin/perl -w
use strict;
binmode(STDOUT, ':utf8');
print(join(', ', PerlIO::get_layers(STDOUT)), "\n");
{
my $guard = PoorMansGuard->new(sub {
binmode(STDOUT, ':utf8');
});
binmode(STDOUT, ':raw');
print(join(', ', PerlIO::get_layers(STDOUT)), "\n");
}
print(join(', ', PerlIO::get_layers(STDOUT)), "\n");
package PoorMansGuard;
sub new {
my ($class, $sub) = #_;
bless { sub => $sub }, $class;
}
sub DESTROY {
my ($self) = #_;
$self->{sub}->();
}